Consolidated Statement of Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In-Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Noncontrolling Interests	Series I Preferred Stock Preferred Stock
Beginning Balance at Dec. 31, 2017	$ 6,589,454	$ 939	$ 4,968,338	$ (124,049)	$ 18,604	$ 1,139,329	$ 364,361	$ 221,932
Beginning Balance (in shares) at Dec. 31, 2017		92,803
Adjusted Balance at Dec. 31, 2017	7,159,978	$ 939	4,968,338	(124,049)	18,604	1,709,853	364,361	221,932
Increase (Decrease) in Stockholders' Equity
Net income	213,168					212,797	371
Other comprehensive loss	14,018				14,018
Preferred dividends	(7,475)					(7,475)
DRSPP proceeds (in shares)		1
DRSPP proceeds	64		64
Conversion of units of the Operating Partnership to common stock (in shares)		15
Conversion of units in the Operating Partnership for common stock	1,560		1,560
Reallocation of noncontrolling interest in the Operating Partnership	(4,493)					(4,493)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)		(20)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	8,090		8,090
Repurchases of common stock (in shares)		(7,133)
Repurchases of common stock	(693,091)	$ (72)	(382,080)			310,939
Proceeds from stock options exercised (in shares)		59
Proceeds from stock options exercised	5,637	$ 1	5,636
Contributions to consolidated joint venture interests	1,828						1,828
Deconsolidation of partially owned entity	(314,596)						(314,596)
Cash distributions to noncontrolling interests	(724)						(724)
Cash distributions declared (per common share, none of which represented a return of capital for federal income tax purposes)	(141,908)					(141,908)
Ending Balance at Jun. 30, 2018	6,242,056	$ 868	4,601,608	(124,049)	32,622	1,457,835	51,240	221,932
Ending Balance (in shares) at Jun. 30, 2018		85,725
Beginning Balance at Dec. 31, 2017	6,589,454	$ 939	4,968,338	(124,049)	18,604	1,139,329	364,361	221,932
Beginning Balance (in shares) at Dec. 31, 2017		92,803
Adjusted Balance at Dec. 31, 2017	7,159,978	$ 939	4,968,338	(124,049)	18,604	1,709,853	364,361	221,932
Increase (Decrease) in Stockholders' Equity
Preferred dividends	(11,213)
Ending Balance at Sep. 30, 2018	6,267,175	$ 867	4,602,650	(124,049)	36,299	1,476,959	52,517	221,932
Ending Balance (in shares) at Sep. 30, 2018		85,594
Beginning Balance at Dec. 31, 2017	6,589,454	$ 939	4,968,338	(124,049)	18,604	1,139,329	364,361	221,932
Beginning Balance (in shares) at Dec. 31, 2017		92,803
Adjusted Balance at Dec. 31, 2017	7,159,978	$ 939	4,968,338	(124,049)	18,604	1,709,853	364,361	221,932
Ending Balance at Dec. 31, 2018	5,947,855	$ 847	4,508,685	(124,049)	15,108	1,278,998	46,334	221,932
Ending Balance (in shares) at Dec. 31, 2018		83,684
Beginning Balance at Jun. 30, 2018	6,242,056	$ 868	4,601,608	(124,049)	32,622	1,457,835	51,240	221,932
Beginning Balance (in shares) at Jun. 30, 2018		85,725
Increase (Decrease) in Stockholders' Equity
Net income	91,811					91,947	(136)
Other comprehensive loss	3,677				3,677
Preferred dividends	(3,738)					(3,738)
DRSPP proceeds (in shares)		0
DRSPP proceeds	52		52
Conversion of units of the Operating Partnership to common stock (in shares)		0
Conversion of units in the Operating Partnership for common stock	0		0
Reallocation of noncontrolling interest in the Operating Partnership	11,941					11,941
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)		13
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	4,634		4,634
Repurchases of common stock (in shares)		(253)
Repurchases of common stock	(25,236)	$ (2)	(13,579)			11,655
Proceeds from stock options exercised (in shares)		109
Proceeds from stock options exercised	9,936	$ 1	9,935
Contributions to consolidated joint venture interests	3,072						3,072
Deconsolidation of partially owned entity	(520)						(520)
Cash distributions to noncontrolling interests	(1,139)						(1,139)
Cash distributions declared (per common share, none of which represented a return of capital for federal income tax purposes)	(69,371)					(69,371)
Ending Balance at Sep. 30, 2018	6,267,175	$ 867	4,602,650	(124,049)	36,299	1,476,959	52,517	221,932
Ending Balance (in shares) at Sep. 30, 2018		85,594
Beginning Balance at Dec. 31, 2018	5,947,855	$ 847	4,508,685	(124,049)	15,108	1,278,998	46,334	221,932
Beginning Balance (in shares) at Dec. 31, 2018		83,684
Increase (Decrease) in Stockholders' Equity
Net income	210,470					212,370	(1,900)
Acquisition of subsidiary interest from noncontrolling interest	(25,791)		(515)				(25,276)
Other comprehensive loss	(43,503)				(43,503)
Preferred dividends	(7,475)					(7,475)
DRSPP proceeds (in shares)		3
DRSPP proceeds	263		263
Conversion of units of the Operating Partnership to common stock (in shares)		5
Conversion of units in the Operating Partnership for common stock	446		446
Reallocation of noncontrolling interest in the Operating Partnership	(14,028)					(14,028)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)		(17)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	10,533		10,533
Repurchases of common stock (in shares)		(1,265)
Repurchases of common stock	(109,313)	$ (12)	(68,203)			(41,098)
Contributions to consolidated joint venture interests	50,692						50,692
Cash distributions to noncontrolling interests	(271)						(271)
Cash distributions declared (per common share, none of which represented a return of capital for federal income tax purposes)	(140,377)					(140,377)
Ending Balance at Jun. 30, 2019	5,879,501	$ 835	4,451,209	(124,049)	(28,395)	1,288,390	69,579	221,932
Ending Balance (in shares) at Jun. 30, 2019		82,410
Beginning Balance at Dec. 31, 2018	5,947,855	$ 847	4,508,685	(124,049)	15,108	1,278,998	46,334	221,932
Beginning Balance (in shares) at Dec. 31, 2018		83,684
Increase (Decrease) in Stockholders' Equity
Preferred dividends	(11,213)
Ending Balance at Sep. 30, 2019	5,763,300	$ 826	4,407,667	(124,049)	(40,132)	1,225,904	71,152	221,932
Ending Balance (in shares) at Sep. 30, 2019		81,515
Beginning Balance at Jun. 30, 2019	5,879,501	$ 835	4,451,209	(124,049)	(28,395)	1,288,390	69,579	221,932
Beginning Balance (in shares) at Jun. 30, 2019		82,410
Increase (Decrease) in Stockholders' Equity
Net income	36,271					36,895	(624)
Acquisition of subsidiary interest from noncontrolling interest	(54)		(54)				0
Other comprehensive loss	(11,737)				(11,737)
Preferred dividends	(3,738)					(3,738)
DRSPP proceeds (in shares)		0
DRSPP proceeds	39		39
Conversion of units of the Operating Partnership to common stock (in shares)		0
Conversion of units in the Operating Partnership for common stock	25		25
Reallocation of noncontrolling interest in the Operating Partnership	(1,481)					(1,481)
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings (in shares)		21
Deferred compensation plan and stock awards, net of forfeitures and tax withholdings	5,948		5,948
Repurchases of common stock (in shares)		(916)
Repurchases of common stock	(74,531)	$ (9)	(49,500)			(25,022)
Contributions to consolidated joint venture interests	2,404						2,404
Cash distributions to noncontrolling interests	(207)						(207)
Cash distributions declared (per common share, none of which represented a return of capital for federal income tax purposes)	(69,140)					(69,140)
Ending Balance at Sep. 30, 2019	$ 5,763,300	$ 826	$ 4,407,667	$ (124,049)	$ (40,132)	$ 1,225,904	$ 71,152	$ 221,932
Ending Balance (in shares) at Sep. 30, 2019		81,515